My primary incentive is to see the story of the FF14 world and experience the encounters. That's why I did coil and that's why I did my Zeta and Anima weapons. I rarely worry about ilvl beyond what I need to do said content, though since I have had a friend ask for me to fill in a gap in his static that has changed somewhat in the last couple of days. Regardless, gear, for me, is always a means to an end beyond its appearance and likewise, beyond appearance, transitory.

Horizontal progression I generally find tiresome. It tends to be a lot of grind for little real progress in my experience. Progression, after all, tends to be simply a gating mechanism, which is why the ease of acquiring gear gets easier as time goes on. Horizontal progression tends to suffer from grindiness because while in Vertical Progression rewards devalue, in Horizontal progression they generally don't. That sounds good until it becomes necessary to get all those rewards to progress meaning if your late to the game you have a massive mountain to climb before you can be on par with the endgame players.

In the end neither system is perfect but I like the system FF14 uses.

Oh by the way I think you misunderstand what a mid-core player is. I mid-core player is interested in content that is challenging but not unforgivingly so. They don't want it to be too easy because that's boring but they don't want it to be too hard because that can just be frustrating and stressful. That's why its called mid-core, because its halfway between casual easy content and Hardcore highly challenging content.